1. Field of the Invention
The present invention relates to a pretreatment process of wood veneer to enhance the cross-grain pliability of the material.
2. Description of the Prior Art
Tenderizing of wood veneer is a known process for enhancing the cross-grain pliability of the material and eliminating tendencies to cup or curl. Such tenderizing also expands the material's utility as making it applicable to mildly warped and compound curved surfaces.
As a process, tenderizing fractures many, but not all, of the cross-grain wood cells that hold the longitudinal grains together. The longitudinal wood grains which are the dominate source of wood strength and beauty are undisturbed.
Tenderizing technique includes the steps of forcing cross-grain conformity of a wood sheet to the surface of a small radius curve whereby cross-grain rays of wood fiber are broken at the veneer surface. A multiplicity of grain parallel cracks are developed that are usually less than half the sheet thickness in depth. When bonded to a rigid, relatively flat substrate surface, such longitudinal veneer cracks are imperceptible.
A prior art apparatus for veneer tenderizing is disclosed in U.S. Pat. No. 2,974,697 issued to A. Elmendorf et al. on Mar. 14, 1961. The Elmendorf et al. apparatus includes a three line roller nip through which a discrete length of veneer sheet is drawn in the cross-grain direction. The roller nip is parallel to the grain direction. As the sheet is drawn into the nip, it is forced around the curvature of a first roll to fissure the veneer surface on one face and around a second roll to fissure the opposite face. The third roll of the set drives the sheet back into the plane of the feed table to force conformity of the sheet to the second roll curvature.
Although the Elmendorf et al. apparatus successfully tenderizes both faces of a veneer sheet in a single pass, the length of a suitable sheet is necessarily limited by the fixed length of the nip rolls. This is an inherent limitation to use of the machine for tenderizing longer sheets as are shaved by veneer cutting machines.
It is, therefore, an object of the present invention to provide a tenderizing method and machine that will process veneer sheets of great or indefinite length.
Another object of the invention is to provide a veneer tenderizing method and machine that will process a veneer sheet longitudinally with the grain direction.